The present application relates to electrical appliances which use batteries. While it finds particular application to battery chargers, it is also applicable to battery powered electrical devices.
Recent years have seen a proliferation of battery powered electrical devices. Digital cameras, personal digital assistants (PDAs), hand held games, portable audio players, remote control devices, wireless computer keyboards and mice, and mobile telephones are but a few examples of this trend.
Rechargeable (secondary) batteries, such as nickel-metal hydride (NiMH), nickel-cadmium (NiCd), and lithium ion (LiIon) electrical cells, have likewise gained increasing acceptance as a renewable power source for these and other devices. Rechargeable batteries are typically well-suited for use in relatively high-drain devices, making them attractive in a wide variety of applications. As they can be recharged and reused, rechargeable batteries can also provide convenience and cost advantages relative to non-rechargeable (primary) batteries.
One factor which can affect the acceptance of rechargeable batteries is the convenience and ease of use of the charger needed to charge them. To provide a reliable electrical connection to the batteries being charged, the charger's battery contacts exert a compressive force on the battery terminals. When inserting a battery for charging, however, it is necessary to overcome this contact force. The contact force must likewise be overcome when removing the battery from the charger. Unfortunately, the contact force can make it difficult to insert and/or remove the batteries, especially where there is limited access to the batteries, if the batteries are otherwise difficult to grasp, or where the user has limited strength or dexterity.
Still another factor which can affect the convenience of the charger is the need to insert the batteries in the proper polarity. This is especially true where the charger provides few visual or physical cues as to the proper battery orientation, under low light conditions, or where the user has limited technical expertise or is otherwise uncomfortable with the charging process.
Other considerations include the flexibility and size of the charger. For example, many users have a number of battery powered appliances, each requiring different size batteries. Consequently, a charger which is able to charge batteries of different sizes has the potential to provide significant cost and convenience advantages. Again, the convenience of the charger is enhanced where the charger is readily configured to accept the different size batteries. At the same time, it is generally desirable that charger be relatively compact, even for chargers which are intended primarily for use in a fixed location.